The present invention relates to a cylinder lock and key.
As known, cylinder locks are formed by a lock cylinder which rotatably contains a plug. At least one row of blind holes is defined inside the lock cylinder, and at least one row of through holes and a key slot are defined in the plug.
Pins are accommodated in said through slots, and one of their ends protrudes into the slot; tumbler pins, supported by springs, are accommodated in the blind holes. The respective key has a row of teeth defined along an edge of the shank which is inserted in the lock. The row of pins of the plug engages between the teeth of the key when said key is fully inserted in the slot, causing the alignment of the plane of contact between the pins and the tumbler pins in the plane of contact between the plug and the cylinder.
The plug can thus rotate in the cylinder, causing the rotation of the bit and the opening of the door.
The disadvantage of this type of lock and key is that it can be easily subjected of fraudulent tampering with tools such as picks which are inserted in the key slot to act on the accessible ends of the pins and move the plane of contact between the pins and the tumbler pins into the plane of contact between the plug and the cylinder.
In order to prevent lock picking as much as possible, appropriately offset ridges are defined in the key slot and hinder action on the pins. However, the key slot, due to manufacturing reasons and to reasons of mechanical resistance of the key itself, is still too wide to constitute an effective barrier against effraction attempts of the described type.